Iron ore such as fine ore and lump ore is reduced in solid phase at, for example, approximately 1000° C. by modified natural gas to obtain direct reduced iron (DRI: Direct Reduced Iron). In the direct reduction iron making method, reduction furnace flue gas is returned to the reducing gas flow to be reused. Accordingly, efficiency is increased.
Water (H2O) and carbon dioxide (CO2) that are produced in the reduction furnace are inert in the reduction furnace. Therefore, it is necessary to remove them when the reduction furnace flue gas is reused. The water is removed in a cooler or scrubber, and the carbon dioxide in, for example, a removal unit with an amine-based solvent or the like (Patent Literature 1).